Development of high-utilization honeycomb-like α-Ni(OH) for asymmetric supercapacitors with excellent capacitance.

The low utilization rate of active materials has been a critical obstacle for the industrialization of ultracapacitors. In this study, a thin layer of cross-structured ultrathin α-Ni(OH) nanosheets was successfully grown on the surface of a nickel foam as a high-conductivity framework by a vibratory water bath route under a low temperature (80 °C) and mild conditions. Combining the ultrathin α-Ni(OH) nanosheets and ultrashort electron transport, the strategy of a perfect intercalation structure of α-Ni(OH) and a thin layer of active material on a continuous conductive framework resulted in a high utilization rate of active material, which further achieved high specific capacitance of 213.55 F g at 1 A g in a two-electrode system and high capacitance retention from three to two electrode system (753.79 F g at 1 A g in the three-electrode system). Meanwhile, the device also achieved high energy density of 74.94 W h kg at power density of 197.4 W kg and still retained 24.87 W h kg at power density of 3642 W kg.